1. Field of the Invention
The present invention relates to a dry electrophotographic image forming apparatus in which replacement of a developer supply container is enabled, such as in a copying apparatus, a printing apparatus, or a facsimile apparatus.
2. Description of the Related Art
In an image forming apparatus of this type, replenishment of a developer in an image forming unit is performed by using a developer supply container when the developer ratio (T/D) in a developer tank is lowered. The work of replacing the developer supply container is often conducted by the user.
In an image forming apparatus of the conventional art, printing is sometimes performed with exceeding the lifetime of a developer, with the result that the printing quality becomes unstable.
In the case such as that where plural image forming apparatuses are disposed in one place, it is often that developers of the apparatuses are different in kind from each other. Even when photosensitive members of the same kind are used, for example, a developer for the analog method (positive development method) is opposite in polarity to that for the digital method (reversal development method). Even in developers of the same polarity, their components (CCA (charge control agent), resins, and the like) are varied in accordance with the charging characteristics (saturated charging quantity), whereby the resistances of the developers are made different from one another. In the case of color image formation, furthermore, the hue is different among black toner, red toner, etc.
When a developer which is non-interchangeable among the apparatuses is erroneously supplied to another apparatus by the user, this supplied developer causes the carrier to be consumed, and the developer to be blown out, with the result that troubles such as that the developer is scattered in the apparatus, and that the photosensitive member is deteriorated occur.
In order to solve these problems, a method is often used in which the shape of a container for a developer is changed in accordance with the kind of the apparatus in which the developer can be used, thereby preventing the container from being erroneously inserted.
When this method is employed, however, plural kinds of containers of different shapes must be prepared, and the production cost is therefore increased.
Japanese Examined Patent Publication JP-B2 4-62075 (1992) discloses a technique in which, when a developer supply container is attached to an apparatus, information (the replenishment quantity, the lot number, and the like) of a developer which is stored in a memory of the container is stored into a memory of the apparatus, and process conditions of image formation are changed in accordance with the information and the consumed quantity of the developer.
In the disclosed technique, the information stored in the developer supply container is used only for changing process conditions of image formation, and it is not judged whether the developer in the container attached to the apparatus is usable or not. Therefore, the technique cannot solve the above-discussed problem of erroneous insertion.